Fungi

Fungi constitute a kingdom of eukaryotic, heterotrophic organisms that include yeasts, molds, and mushrooms. They obtain nutrients by absorbing organic material from their surroundings after secreting enzymes that break down complex substrates. Most fungi grow as networks of filaments called hyphae that form a visible mass known as a mycelium. The cell walls of fungi contain chitin, a strong and flexible carbohydrate.

Fungal life cycles typically involve production of spores for dispersal. Reproduction can be asexual or sexual, and many fungi pass through a dikaryotic stage after hyphal fusion before forming fruiting bodies that release spores. Basidiomycetes produce basidiospores, while ascomycetes produce ascospores; yeasts reproduce by budding or fission.

Ecologically, fungi occupy diverse niches. They are key decomposers, breaking down dead organic matter and recycling carbon and nutrients. Many form mutualistic associations with plants (mycorrhizae) or with photosynthetic partners in lichens. Some fungi are pathogens of plants or animals, including humans, and can cause diseases.

Diversity and distribution: estimates suggest millions of fungal species, though only about 120,000 described to date. Fungi inhabit virtually every environment, especially moist terrestrial habitats and decaying matter, but can also be aquatic or extreme environments.

Humans rely on fungi for food, medicine, and industry. Yeasts drive bread and alcoholic fermentation; molds and mushrooms contribute to cuisine and food processing. Fungi produce antibiotics (for example, penicillin) and industrial enzymes. However, some species are poisonous, and others act as agricultural or medical pathogens.

Conservation and research: fungal diversity is threatened by habitat loss and climate change, while new species and biotechnological applications continue to be discovered through molecular and ecological studies.